Photosynthesis takes in the carbon dioxide produced by all breathing organisms and reintroduces oxygen into the atmosphere. Photosynthesis is how plants make their own food and get energy .plants need the things for photosynthesis carbon dioxide ,water and sunlight . Carbon dioxide is taken in by the leaves of a plant . Water is taken by the leaves of a plant . Water is taken by the root of a plant ,energy from sunlight works together with the carbon dioxide and water to make sugar and oxygen . The sugar is used as food for the plant .The oxygen goes out of the leaves .